IS: 2386 - Part 4 

1. Introduction

The Los Angles abrasion test is a common test method used to indicate the toughness and abrasion characteristics of aggregates. The abrasion characteristics of aggregates are important because the durability of bituminous mix depends on the resistance of the aggregate to crushing, degradation and disintegration. This method covers the procedure for determining the resistance to degradation of aggregates using Los Angeles Abrasion testing machine.

2. Apparatus

(i) Los Angeles machine which consists of a hollow cylindrical drum closed at both ends with an inner dia of 700 mm and inside length 500 mm, capable of rotating about its horizontal axis.

The cylinder shall be supported on sides by stub shafts but not entering inside.

NOTE: The shaft bearing shall be mounted on concrete or any rigid support. 

The drum shall rotate along a horizontal axis. An opening is provided on the drum to introduce sample inside. A suitable dusttight lid keeps the opening closed while drum is rotating.

A removable steel shelf of depth 88 mm and suitable thickness preferably made with wear resistant steel, extending to the full length of the drum and projecting inward is mounted on the interior cylindrical surface. The steel shelf is fixed rigidly to the inside of the drum.  The position of the shelf is such that sample and spheres shall not impact on the lid of the opening or be near it. If the shelf is found bent in either direction, it shall be replaced.

NOTE: The suggested power for motor is 1 HP. 

(ii) A straight metal tamping rod of circular cross section, 1.0 cm in dia and 23.0 cm long, rounded at one end.

(iii) IS test sieves of sizes 40 mm, 25.0 mm, 20 mm, 12.5 mm, 10 mm, 6.3 mm, 4.75 mm, 2.36 mm and 1.70 mm.

(iv) A balance of capacity not less than 6000 gm with sensitivity of 0.1 gm.

(v) The charge consisting of steel spheres of approximately 48 mm dia and having a mass between 390 and 445 g. Six to twelve balls are required for the test.

(vi) Drying oven, thermostatically controlled capable of maintaining temperatures of 110±5oC.

3. Preparation of sample for testing

a) The aggregate samples are prepared in four grading as given below depending upon the maximum size of aggregate. 

IS sieve size mm     Mass required in        gm for each grading  
Passing Retaining A B C D E F G
80 63         2500±50    
63 50         2500±50    
50 40         5000±100 5000±100  
40 25 1250         5000±100 5000±100
25 20 1250            
20 13 1250 2500          
13 10 1250 2500          
10 6.3     2500        
6.3 4.8     2500        
4.8 2.4       5000      

b) The amount of charge to be added to the aggregate depending on the grading of the sample is given below

Grading No of spheres Total weight of the charge
A 12 5000±25
B 11 4584±25
C 8 3330±20
D 6 2500±15
E 12 5000±25
F 12 5000±25
G 12 5000±25

4. Procedure

a) Wash and oven dry the test samples of aggregate to constant mass at 110±5°C and cool to room temperature.

b) Separate into different fraction and combine to get the required grading.

c) Place the aggregate and the required charge inside the Los Angeles testing machine and rotate at a speed of 30 to 33 revolutions per minute.  

d) For grading A, B, C and D, machine shall be rotated for 500 revolutions and for E, F and G it shall be rotated for 1000 revolutions.

e) After completion of the revolutions, make a preliminary separation using 1.70 mm IS sieve.

f) Wash the material retained on 1.70 mm sieve and dry to constant mass in an oven at 110±5°C. Find the weight to the nearest 1 gm.  

NOTE: Elimination of washing seldom varies the result by more than 0.2% of the original sample mass.  

NOTE: The test may be carried out in two stages:

(i)  After 100 revolutions, the sample is taken out and sieved in 1.70 mm sieve without washing to determine the amount of degradation.

(ii) The sample including all fines is carefully collected, returned to the machine and for the remaining 400 revolutions required to complete the test.  It is observed that the ratio of loss at 100 revolutions to 500 revolutions should not greatly exceed 0.2 for material of uniform hardness. 

5. Calculations

The Los Angeles Abrasion value is expressed as a percentage of the loss of weight against the weight of sample tested.

Let the weight of sample taken = W1 gm.

Weight of material retained in 1.70 mm sieve = W2 gm.

Loss of material due to abrasion = W1 – W2

Los Angeles abrasion value = (W1 – W2/W1) x 100 percent.

The result is reported to the nearest 1% by mass.